The present invention relates to the art of illumination devices useful in general lighting applications and, more particularly, relates to an optical commutator useful in specialized fiber optic lighting applications such as, for example, lighting applications which require convenient, efficient, high intensity, small spot size lighting. However, the invention is applicable in any situation where flexible light piping is required, and the incorporated light source may include incandescent, fluorescent, laser, or other light sources.
Electrical lamp apparatus have been in existence at least since the invention of the incandescent light bulb. Many modern electric lamps still utilize incandescent sources essentially similar to the original design but incorporating improved filament materials, better electrical current and voltage control, improved vacuum quality, and other improvements. Other modern lamp apparatus employ fluorescent light sources which typically exhibit higher efficiency and longer service life versus incandescent sources. Specialty lamps are also available which use novel sources such as gas discharge tubes using mercury, sodium, or other gas vapors, xenon arc lamps, gas lasers, semiconductor lasers and light emitting diodes (LED""s), and other optical sources.
Beyond the light source, the properties of a lamp system are dictated primarily by the optical path design. In the simplest case, there may be no defined optical path, for example, a ceiling fluorescent tube with no associated optical components other than light diffusers, filters, or the like. More commonly, the omni directional light output is conditioned through the use of parabolic reflectors, flat reflectors, lenses or other refractive elements, diffusers such as lamp shades, spectral filters, apertures, and the like.
In the case of a fixed, immobile lamp, a great deal of engineering freedom exists in the design of the optical path. Optical path design options are significantly restricted, however, in cases where the point of light emission must be mounted on a flexible arm so that the direction or physical location of the light emission is adjustable. An example is the desktop lamp, which in the conventional commercial design includes a flexible arm such as a xe2x80x9cgooseneckxe2x80x9d flexible arm, multiple-segment multiple-hinged arm, or the like, and a light emitting head which includes an incandescent or fluorescent light source and associated reflectors or other optical components. Other lamp types which may require flexible mounting and therefore typically incorporate the above-described basic design include surgical operating room lamps and lamps for precision mechanical operations such as semiconductor wire bonding, jewelry work, and other fine mechanical tasks.
The requirements for the light emitting head typically include: high brightness, low temperature operation, small spatial size, and low weight. High intensity is required due to the nature of many applications, such as reading and precision jewelry work. Preferably, the lighthead temperature is close to ambient temperature, especially for applications such as desk lighting where the lighthead will be close to a user""s face and hands. A small lighthead size is preferable for flexibility in positioning. Low weight is preferable to reduce the mass and cost of the weight-bearing flexible arm.
Conventional lamp designs employing a flexible arm and attached head containing at least the light source require undesirable engineering design compromises between light intensity, thermal temperature, size, and weight. The desired high intensity sources are usually larger and heavier than lower intensity sources. High intensity sources also tend to generate a large amount of heat. The heating problem is especially acute for incandescent sources because these sources tend to be rather inefficient. Replacement of incandescent bulbs by fluorescent tubes may greatly reduce the operating temperature, typically with an accompanying decrease in light intensity which may however be acceptable for certain applications. Improved optics which provide better coupling of the generated light to the area requiring illumination are also beneficial, but the optics may also increase head size and weight.
A different solution to the need for a flexible lighting source has become available with the advent of fiber optics. Using fiber optical transmission permits decoupling of the light source from the point of light emission. A design incorporating fiber optics may include a large, hot, heavy, high intensity light source positioned remotely from a light emitting head. The head is movably located at the point of light emission and is connected to the light source by a fiber optical link. The head need only contain those optical components such as reflectors, lenses, and the like which are necessary to shape the fiber optical output appropriately for the application. Certain optical components, such as spectral filters, may be placed near the light source remote from the head. An additional advantage of incorporating fiber optical transmission is that a single light source may provide optical power for a number of flexibly positioned heads. Such a system could be valuable, for example, in a hospital operating room where the surgical area may preferably be illuminated from two or more different angles to reduce shadowing.
In spite of the benefits potentially available through the incorporation of fiber optics into flexibly positioned lighting systems, practical difficulties have resulted in limited use of fiber optics in such systems. A critical issue is light transmission efficiency at fiber coupling points. Efficient coupling between adjacent fibers requires similar or preferably identical fiber core sizes, smooth fiber end cleaves preferably including anti-reflection coatings, and extremely precise axial and angular alignment of the two fiber tips. For a flexible lamp, the close axial and angular alignment must be maintained as the lamp arm is moved and rotated about the mechanical joints where the fiber coupling typically is employed.
The prior art teaches using standard threaded and snap connectors for connecting fiber optical segments. However, there is a need for a convenient and reliable mechanical configuration for providing a fully rotatable fiber coupling where one fiber end may be rotated freely with respect to the other fiber end while maintaining efficient optical coupling. Such an optical coupling may conveniently be called an xe2x80x9coptical commutatorxe2x80x9d in close analogy to the electrical commutator typically employed in connection of rotor windings in electric motors and generators. An optical commutator having a high light transmission efficiency is a highly desired and critical element for lamp designs in which an arm bearing a fiber-coupled light emitting head is to be freely rotatable about a joint.
It is further desired to provide an optical commutator that finds application well beyond lighting systems. Fiber optics are used increasingly in communications and in various medical applications, among others. The optical commutator is applicable to desired areas identified above as well as others where rotatable coupling of fiber segments may be desirable.
In accordance with one aspect of the present invention, a rotatable optical fiber coupler for coupling a first fiber with a second fiber is provided. A first hollow radially symmetric connector has a threaded first end and a second end having a plurality of resilient springy fingers extending therefrom in the axial direction, the fingers having extensions directed radially inward. A second hollow radially symmetric connector has a threaded first end, the second connector also having a circumferential groove on the outer surface. The second connector detachably attaches coaxially to the first connector by spring force pressing the finger extensions of the first connector into the groove of the second connector, whereby the second connector may rotate about the coaxial axis relative to the first connector.
A first sleeve is positioned over a length of the first optical fiber and is received into an opening in the threaded end of the first connector, the first sleeve pressing against the first connector and against the first fiber. A second sleeve is positioned over a length of the second optical fiber and is received into the second connector, the second sleeve pressing against the second connector and against the second fiber.
A first bushing securely fits into a space in the second end of the first connector and receives an end of the first fiber after the fiber jacket and a portion of the fiber cladding has been stripped from said end. The first bushing has an inner lip against which the first fiber end presses. A second bushing securely fits into a space in a second end of the second connector and receives an end of the second optical fiber after the fiber jacket and a portion of the fiber cladding has been stripped from said end. The second bushing has an inner lip against which the second fiber end presses.
A first compression fitting is provided to secure the first fiber end to the first connector. The first compression fitting includes a split ferrule ring which fits onto the first sleeve, and a ferrule nut which accepts the split ferrule ring and threads onto the threaded first end of the first connector, whereby the first sleeve distributively compresses against the first fiber end and secures the first fiber end in the first connector.
A second compression fitting is provided to secure the second fiber end to the second connector. The second compression fitting includes an insert with a flange which presses against the second sleeve. A nut accepts the flange of the insert and threads onto the threaded first end of the second connector, whereby the flange compresses against the second sleeve and compressively secures the second fiber end in the second connector
In accordance with another aspect of the present invention, an optical commutator for coupling a second fiber end to a first fiber end in a detachable rotatable manner is disclosed. A second connecting piece is essentially tubular in shape. The second fiber end is inserted completely through the second connecting piece and held rigidly therein such that the second fiber end is set back a preselected distance. A first connecting piece is essentially tubular in shape and essentially divided along the axial direction into a first portion into which the first fiber end is inserted and held rigidly, and a second portion into which a portion of the second connecting piece is coaxially detachably inserted and rotatably attached therein. The first portion and the second portion are apportioned such that the first fiber end is coaxial with and in close proximity to the second fiber end whereby light coupling across the fiber ends is obtained.
Preferably, the detachable attachment of the second connecting piece to the first connecting piece second portion includes an axially symmetric groove on an outer surface of the second connecting piece, and an axially symmetric protrusion on an inner surface of the second portion of the first connecting piece which essentially mates with the axially symmetric groove of the second connecting piece.
One advantage of the present invention is that a fully rotatable light-emitting head may remain cool during operation independent of the temperature of the light source.
Another advantage of the present invention is that it decouples the light-emitting head from the light source of a flexibly positioned lighting source.
Another advantage of the present invention is that it permits full rotation of an arm bearing a light-emitting head about any angle, even including angles beyond 0xc2x0-360xc2x0, i.e. multiple turn rotation.
Another advantage of the present invention is that it provides a rotatable fiber coupling which is easily detachable.
Another advantage of the present invention is that it facilitates a modular lighting system wherein multiple detachable lighting fixtures are available for different applications.
Yet another advantage of the present invention is that it efficiently couples light via fiber optical connection from a light source through a fully, continuously rotatable joint in a lamp arm.
Still further advantages and benefits of the present invention will become apparent to those of ordinary skill in the art upon reading and understanding the following detailed description.